This document summarizes a presentation about building scalable apps with Google App Engine. It discusses the history and capabilities of App Engine, including how it provides developers with a cloud platform that handles hardware, networking, operating systems, runtimes and more. App Engine automatically scales apps across Google's infrastructure and provides tools to deploy and manage apps with high availability and performance.

1. Building Scalable Apps with
Google App Engine
David Chandler
Developer Programs Engineer
drfibonacci@google.com
CloudDevDay Detroit
Jun 11, 2011
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2. Agenda
A word about the cloud
A Brief History of App Engine
Building with App Engine
What’s New in App Engine
Q&A
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3. 3
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4. What is SaaS
cloud
computing? PaaS
IaaS
Software…
Platform…
Infrastructure…
Postage
Place
Here
… as a Service
4
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5. App Engine is part of Google’s cloud platform
SaaS
PaaS
IaaS
Source: Gartner AADI Summit Dec 2009 Google Confidential and Proprietary 5
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6. Google's Cloud Offerings
Your Apps
Google Apps
Third party Apps:
Google Apps Marketplace
SaaS ________
Google App Engine
PaaS
Google Storage
Prediction API
IaaS
BigQuery
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7. Not all "Platforms" are alike
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8. Cloud development in a box
Hardware
Networking
Operating system
Application runtime
• Java, Python
Static file serving
Services
Fault tolerance
Load balancing
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9. What is Google App Engine?
Business: Google’s cloud computing platform
Technical: giant Web farm in front of world’s largest HashMap
Java developer: easiest and most scalable Java hosting environment
Startup developer: FREE to get started
App Engine expresses how Google thinks about infrastructure
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10. Let’s do it
Sign up for AppEngine beta
Install Google Plugin for Eclipse
Create new Google Web application
Deploy it
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11. What did we actually do?
Hot deployed an exploded WAR file
NO server setup
NO instance to provision
NO networking
NO J2EE config
NO start/stop
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12. What makes AppEngine special?
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13. BigTable: a Distributed Storage System
Fay Chang, Jeffrey Dean, Sanjay Ghemawat, Wilson C. Hsieh, Deborah A. Wallach, Mike Burrows,
Tushar Chandra, Andrew Fikes, and Robert E. Gruber
Abstract
Bigtable is a distributed storage system for managing structured data that is designed to scale to a
very large size: petabytes of data across thousands of commodity servers. Many projects at Google
store data in Bigtable, including web indexing, Google Earth, and Google Finance. These
applications place very different demands on Bigtable, both in terms of data size (from URLs to web
pages to satellite imagery) and latency requirements (from backend bulk processing to real-time data
serving). Despite these varied demands, Bigtable has successfully provided a flexible, high-
performance solution for all of these Google products. In this paper we describe the simple data
model provided by Bigtable, which gives clients dynamic control over data layout and format, and we
describe the design and implementation of Bigtable.
Appeared in:
OSDI'06: Seventh Symposium on Operating System Design and Implementation,
Seattle, WA, November, 2006.
http://labs.google.com/papers/bigtable.html
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14. High Replication Datastore
Default when you create a new app
Actively replicated to multiple data centers
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15. No servers to configure
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16. Easy deployment
OR
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17. Powerful admin console
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18. Distributed frontends
Edge Caching
Priority routing
Geographically close connection
endpoint
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19. Free to get started
6.5 CPU hrs/day
1 GB storage
650K URL Fetch calls
2,000 recipients emailed
1 GB/day bandwidth
100K tasks
$0.72 backend usage (9h on small instance)
~5M pageviews / month
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20. A Brief History of App Engine
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21. App Engine Growth
2008 2009 2010 2011
App Engine Launch Batch write/read Java Task Queues Blobstore Multitenancy Hi-Replication
Python Https DB Import XMPP Appstats Instance Console Datastore
Datastore Status- cron incoming email cursors Always On Backends!
Memcache Dashboard Mapper hi-perf imag Channel API
logs export 10 min tasks Files API
Remote API
Prosp Search
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22. By the Numbers
100,000+
Active Developers
per Month
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23. By the Numbers
200,000+
Active apps per week
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24. By the Numbers
1.5B+
Pageviews per
day
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25. Official Royal Wedding on App
Engine
On Wedding day, served:
• Up to 32k requests per second
• 37.7 million pageviews
• 13.7 million visitors
http://goo.gl/F1SGc
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27. Building with App Engine
∑
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28. Language runtimes
Duke, the Java mascot
Copyright © Sun Microsystems Inc., all rights reserved.
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29. Specialized services
Memcache Datastore URL Fetch
Mail XMPP Task Queue
Images Blobstore User Service
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30. Services are simple
UserService svc = UserServiceFactory.getUserService();
User authenticatedUser = svc.getUser();
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31. Datastore APIs
Native
• DatastoreServiceFactory.getDatastoreService().get(Key key)
• DatastoreServiceFactory.getDatastoreService().put(Entity entity)
• But…entities are not POJOs
JDO, JPA, or third party
• Objectify (http://code.google.com/p/objectify-appengine)
• Twig, SimpleDS, Slim3, others
Objectify example (using DAOBase)
• ofy().put(Person p);
• ofy().get(Person.class, 238749);
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32. Objectify goodies
Light
• 36k jar, no external dependencies
Fast
• no bytecode enhancement on start
Simple
• No PersistenceManager lifecycle means no DI required
• No attach / detach hassle
• No “find to delete”
• No lazy fetching, proxy classes...
@Cache (uses App Engine Memcache)
@Embedded (objects as list tuples)
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33. How to learn Datastore
Understand consistency vs. concurrency tradeoff
• Selective denormalization sometimes required
• Use the power of the platform, don’t try to make it what it isn’t (relational)
 Batch gets / puts
 List properties for fast, lightweight indexes
 Retrieve parent entity from child key
Watch previous Google I/O presentations
• Brett Slatkin 2009 on list properties and million-user fanout
• Book: see GWT Books page at code.google.com
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34. Secure Data Connector (SDC)
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35. How to do background processing?
Your application can’t start threads
• Causes problems for some frameworks
• See will-it-play-in-appengine wiki
• No, you can’t run WebSphere or JBoss on AppEngine
AppEngine provides Task Queue API
• Servlet-based
• Allows throttling
Backends (new!)
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36. Queue a Task
Define queue in WEB-INF/queue.xml
<queue>
<name>mail</name>
<rate>8/m</rate>
</queue>
Create worker servlet that handles task
Queue the task
queue.add(url("/mail").param("key", key)…)
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37. Is there an easier way?
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38. Is there an easier way?
Vince Bonfanti’s Deferred task servlet
Now part of App Engine API!
• com.google.appengine.api.taskqueue.DeferredTask
Task throttling can help with quotas
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39. What’s New In App Engine?
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40. Namespaces API
What’s wrong with this query in a multi-tenant app?
DELETE FROM Transactions
WHERE AcctID = 2347272
DELETE FROM Transactions
WHERE CustID = 2394872 AND AcctID = 2347272
Oops.
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41. Namespaces API
SQL
App
App
Server
Server
public void doFilter(ServletRequest req, ServletResponse resp,
FilterChain chain) throws IOException, ServletException
{
NamespaceManager.set(...);
chain.doFilter(request, response);
}
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42. Namespace API - Memcache
Memcache entry
entries
<app id> <namespace>
<app id> <key> <value>
<key> <value>
<key> <value>
<key> <value>
<key> <value>
<key> <value>
<key> <value>
<key> <value>
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43. Namespaces - Datastore
Row data
<app id> <namespace>
<namespace>
<app id> <kind> <key> <properties>
Single property index
<app id> <namespace>
<namespace>
<app id> <kind> <prop> <value> <key>
Composite Index
<app id> <namespace>
<namespace>
<app id> <kind> <prop1> <prop2> <key>
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44. Channel API
Asynchronous Server ⟺ Client Communication
• Channel-based
• Bi-directional
Server
• Send messages via ChannelService object
• Receive messages in a web hook
Client
• JavaScript library
• Receive server messages in a callback
Built on Gmail chat client (Google Talk)
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45. Channel API demo
www.typrx.com http://code.google.com/p/gwt-gae-channel/
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46. Channel API - Server Interface
/**
* ChannelService allows you to manage two-way connections
* with clients.
*/
public interface ChannelService {
/**
* Creates a channel associated with the provided applicationKey
*/
String createChannel(String applicationKey);
/**
* Sends a ChannelMessage to the client.
*/
void sendMessage(ChannelMessage message);
/**
* Parse the incoming message in request. This method
* should only be called within a channel webhook.
*/
ChannelMessage parseMessage(HttpServletRequest request);
}
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47. Channel API - Client (GWT)
http://code.google.com/p/gwt-gae-channel/
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48. Android Tooling in GPE
In GPE 2.4 beta
• Debug As | Local App Engine Connected Android Application
• Launches Android emulator
• Allows apps in the emulator to call App Engine dev server on localhost
See App Engine + Android session from this year’s Google I/O
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49. App Engine is Leaving Preview (Beta)!
Full Google Product - 3 year deprecation support
99.95% SLA for all paid users
Operational and Developer Support available
New business-friendly Terms of Service
Billing via invoice
Rounded out feature set including Frontend and Backend
capabilities
New sustainable pricing model
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50. SLAs are more than just 9s
SLA is about transparency
HRD does not need planned downtime
Uptime will be measured by 1000s of various probes from
around the globe
Customers will be able to contribute to our metrics
Upcoming Monitoring API to automatically monitor your
own applications
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51. Frontends and Backends
• Instances (running unit for both Frontends and Backends)
o Have set amount of CPU and Memory
o Run your code
• Frontends
o Scale dynamically based on your traffic
 The App Engine Scheduler determines when to spin up or
down Frontend instances
 Controls will be added to allow customers to optimize the
Scheduler for particular usage
• Backends (Launched at I/O with 1.5.0!)
o Run based on admin control
o Choose CPU and Memory size
o Long-running (no 30-sec HTTP request limit)
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52. New Pricing Model Overview
• Usage types:
o Free - similar to today
o Paid - $9/app/mo (+ usage) including SLA
o Premier - $500/account/mo (+ usage) including operational
support
• No more CPU hours
o Charging for size and number of running Frontends/Backends
(incorporating CPU + memory)
o APIs (including Datastore) charged based on operations
• Add-ons
o For example: SSL for custom domains will be available for
monthly fee
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53. Thank you!
http://code.google.com
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